JP2013540520A - Attenuated RF power for automated capsulotomy - Google Patents

Abstract

  The capsulotomy device has a capsulotomy probe configured for insertion into the eye through the incision and a pulse generator configured to send at least one radio frequency (RF) pulse to the capsulotomy probe. The transmitted RF pulse has a predetermined attenuation shape such that the power level of the transmitted RF pulse is substantially attenuated over the duration of the RF pulse. In certain embodiments, the pulse generator is configured to deliver a series of two or more RF pulses to the eye such that the energy of each of the series of subsequent pulses is substantially attenuated relative to the immediately preceding pulse. .

Description

  This application claims the effect of priority of US patent application Ser. No. 12 / 893,149, filed Sep. 29, 2010. The present invention relates generally to the field of cataract surgery and, more particularly, to a method and apparatus for performing a capsulotomy.

  The accepted treatment for cataracts is surgical removal of the lens and replacement of the lens function with an artificial intraocular lens. In the United States, the majority of cataract lenses are removed by a surgical technique called phacoemulsification. Before removing the cataractous lens, the anterior capsule must be opened or incised. During phacoemulsification and suction, the lens nucleus is emulsified while high tension is applied at the incision edge of the anterior capsulotomy. Therefore, continuous excision or laceration (incision) without tags is an important step in safe and effective phacoemulsification therapy.

  If the sac is opened with many small sac lacerations, the remaining small tags can cause radial sac lacerations that spread into the posterior sac. These radial lacerations cause complications because after surgery, the lens becomes unstable after further removal of the cataract and safe replacement of the intraocular lens in the lens capsule. The vitreous can then enter the anterior chamber of the eye when the posterior capsule is further punctured. In this case, the vitreous must be removed by additional treatment with special instruments. Vitreous loss is also associated with an increased probability of secondary retinal detachment and / or infection in the eye. Importantly, these complications can lead to blindness.

  A known equipment used for phacoemulsification suction has an ultrasonically driven handpiece with an attached cutting blade. In some of these handpieces, the working part is centrally located and the hollow resonant bar or horn is attached directly to the set of piezoelectric crystals. Piezoelectric crystals provide ultrasonic vibrations to drive both the horn and the attached cutting blade during phacoemulsification.

  Many of the known devices and methods used for cystotomy treatment require a number of techniques in the role of the surgeon to produce a continuous curvilinear capsulotomy. This is due to the extreme difficulty of controlling the path of the cutting blade of the device. For example, a typical treatment begins with a capsulotomy with a cutting knife, such as the cutting blade described above. The incision is then made circular or oval by pushing the tip of the incision in the sac with a cutting knife such as a wedge rather than an incision shape. Alternatively, the initial sac incision may be torn in a circular shape by grasping the tip with a fine caliber forceset and widening the incision. Either of these methods is a very difficult operation, and the tearing operation can cause undesirable capsular tears to the back of the lens, even for experienced people.

  Furthermore, even if a smooth capsulotomy is finally created without a tag, the size and / or location of the capsulotomy can be problematic. For example, a capsulotomy that is too small can interfere with the safe removal of the lens nucleus and lens cortex and prevent proper insertion of the intraocular lens into the lens capsule. The additional stress required to complete a small or erroneous capsulotomy operation puts the eyes at risk of ciliary ligament breakage and sac breakage. Any of these complications can increase the length and complexity of the surgery and may cause the vitreous to disappear.

  Continuous, properly placed and circular incisions are (1) significant reduction of radial damage and tags in the anterior capsule, (2) sac integrity required for proper central placement of the lens prosthesis, ( This is very suitable because it results in 3) safe and effective hydrodissection, (4) safe use of sac treatment in patients with poor vision sac and / or patients with small pupil openings. In addition, the capsulotomy must be dimensioned appropriately to the diameter of the implanted intraocular lens to reduce the risk of secondary cataracts, also called posterior capsule opacification, and the proposed accommodative eye It must also be properly dimensioned for use with the inner lens design. Accordingly, there is a continuing need for improved devices for performing an anterior sac incision.

  Various methods and devices have been proposed for automating the capsulotomy process. One method is described in US patent application Ser. No. 12 / 618,805 (hereinafter the '805 application) entitled “Dissection Device Using Pulsed Electric Field” filed on Nov. 16, 2009. It was. The '805 application, the entire contents of which are hereby incorporated by reference, describes a method and apparatus for making a capsulotomy using a high frequency current applied to the anterior lens capsule via a monopolar electrode. The device is placed against the anterior capsule of the eye and is generated using a ring electrode, a pulsed electric field for performing an incision operation, and a ground electrode placed at various positions inside or outside the eye And are used. In some embodiments of this system, the ring electrode comprises a thin, conductive wire. Very small cross sections (e.g., less than about 0.25 millimeters in diameter) provide high strength electric fields in the vicinity of the wire, which further reduce the strength away from the wire. Since a ground electrode having a much larger cross-section than the cutting electrode is used in this system, the electric field remains attenuated at the ground electrode, and a high proportion of possible cutting energy is a narrow area near the wire of the cutting electrode. Remain in.

  Another system is shown in US 2006/0100617, the entire contents of which are hereby incorporated by reference. This publication shows an automatic capsulotomy device with a circular flexible ring made of elastomer, acrylic or thermoplastic material. Incorporated in each of the various embodiments of this flexible ring is local heating on the anterior capsule to define a weakened boundary for easy detachment of the portion of the sac within the annular ring. To produce, a resistive heating element or a pair of bipolar electrodes excited by known techniques. Various other devices have been proposed, many of which are U.S. Pat. No. 6,066,138, patented May 23, 2000, U.S. Pat. No. 4,481,948, filed Nov. 13, 1984, And by cautery elements such as WO 2006/109290 published on October 19, 2006. The entire contents of each reference given in this paragraph are hereby incorporated by reference to provide background and context for the present invention.

  The capsulotomy device has a capsulotomy probe configured for insertion into the eye through the incision and a pulse generator configured to send at least one radio frequency (RF) pulse to the capsulotomy probe. The RF pulse has a predetermined attenuation shape such that the power level of the transmitted RF pulse is substantially attenuated over the duration of the RF pulse. In certain embodiments, the pulse generator is configured to deliver a series of two or more RF pulses to the eye such that the energy of each of the series of subsequent pulses is substantially attenuated relative to the energy of the previous pulse. Is done.

  In some embodiments, the predetermined attenuation shape is an attenuation shape such that the power level of the transmitted RF pulse is attenuated by at least one-half over the duration of the RF pulse. In these and other embodiments, the predetermined attenuation shape is such that the RF pulse delivered in the eye causes bubble nucleation without excessive adhesion or overheating of the capsular bag beyond the intended area. It may be designed to ensure that it occurs. In some embodiments, a series of two or more RF pulses is sent to the eye such that the energy of each of the series of second and subsequent pulses is substantially attenuated relative to the energy of the previous pulse. In some of these embodiments, the amplitude of each of the series of subsequent pulses is substantially attenuated relative to the amplitude of the immediately preceding pulse. In addition, the amplitude of each pulse after the second round is substantially equal to the amplitude of the series of first pulses, but the length of each of the series of pulses after the second round is substantially shorter than the length of the immediately preceding pulse.

  A method is disclosed that includes the use of an intra-pulse attenuation shape where the pulse power is attenuated over the duration of the pulse, or an inter-pulse attenuation shape where the energy of each of a series of pulses is attenuated relative to the energy of the previous pulse. It was. In some embodiments, both techniques are used. Thus, one exemplary method for making a capsulotomy begins with the insertion of a capsulotomy probe into the anterior chamber of the eye and the placement of the capsulotomy probe incision in contact with the anterior lens capsule of the eye. At least one radio frequency (RF) pulse is then sent to the eye through the capsulotomy probe with a predetermined attenuation shape. This shape is such that the power level of the transmitted RF pulse is substantially attenuated over the duration of the RF pulse.

  Another exemplary method begins with the insertion of a capsulotomy probe into the anterior chamber of the eye and the placement of the capsulotomy probe incision in contact with the anterior lens capsule of the eye. A series of two or more radio frequency (RF) pulses are then sent to the eye through the capsulotomy probe such that the energy of each of the series of second and subsequent pulses is substantially attenuated relative to the energy of the previous pulse. It is done. In some embodiments, the use of this interpulse attenuation shape may be combined with the use of an intrapulse attenuation shape.

  In some embodiments, a capsulotomy device for performing the techniques disclosed herein includes a capsulotomy probe configured for insertion into the eye through an incision and an electrical Connected pulse generators. The pulse generator has a predetermined attenuation shape such that the transmitted RF pulse has a predetermined attenuation shape and the power level of the transmitted RF pulse is substantially attenuated over the duration of the RF pulse. It is configured to send at least one radio frequency (RF) pulse to the capsulotomy probe. In certain embodiments, the pulse generator may also send a series of two or more RF pulses to the eye such that the energy of each of the second and subsequent pulses in the series is substantially attenuated relative to the energy of the previous pulse. Composed. In other embodiments, both techniques are used.

  Of course, those skilled in the art will understand that the present invention is not limited to the above features, advantages, circumstances or examples, and upon reading the following detailed description and referring to the accompanying drawings, Understand additional features and benefits.

Fig. 3 shows a capsulotomy device according to some embodiments of the present invention including a pulse generator and a cutting electrode device. Details of the capsulotomy probe are shown. 3 shows a cross section of the annular portion of the probe of FIG. FIG. 5 is a process flow diagram illustrating a method for performing a capsulotomy. It is a block diagram of a pulse generator. Fig. 3 shows a radio frequency pulse having a predetermined attenuation shape. Fig. 4 shows a series of radio frequency pulses that are gradually attenuated. A series of attenuated radio frequency pulses is shown.

  As mentioned above, various methods and devices have been proposed for automating the capsulotomy process. For example, the '805 application, incorporated by reference above, shows a method and apparatus for performing a capsulotomy using a high frequency current applied to the anterior lens capsule through a monopolar electrode. Other capsulotomy probe configurations with resistive heating elements or a pair of bipolar electrodes are possible and are excited by known techniques for producing local heating in the anterior capsule. Known to many of these systems is the use of high energy pulse generators to deliver conditioned pulse energy to the surgical site.

  Those skilled in the art will appreciate the broader applicability of the techniques and apparatus according to the various inventions disclosed herein, which techniques use pulses applied to a heating element placed against the anterior lens capsule. It will be described with reference to the previously disclosed method for making a capsulotomy. One such method is shown in US 2010/0094278, entitled “Sactomy Device With Flexible Heating Element”, the entire contents of which are hereby incorporated by reference. Is taken in. This means uses a resistance heating element formed from a superelastic wire which is annularly formed and has electrical resistance. The heating element is excited with a short pulse or a series of pulses of current. Heating the ring-shaped element burns the lens capsule and effectively provides a smooth incision in the capsule.

  On the other hand, the system shown in the '805 application includes a ring electrode placed on the anterior capsule of the eye and a ground electrode placed on the inside or outside of the eye for performing an open operation. In order to increase the cutting efficiency and reduce the far field effect, the ring electrode is provided with a thin conductive wire. (Diameters less than 25 millimeters) provide high-intensity electric fields in the vicinity of the wires, and these electric fields further reduce the strength of the wires remotely. Thus, a high rate of dissecting energy is applied to the narrow area around the dissecting electrode.

  FIG. 1 illustrates components of an exemplary capsulotomy device according to some embodiments according to the present invention. The illustrated system includes a pulse generator 110 that generates a radio frequency pulse for application to the eye through the dissection electrode 120. 2 and 3 show details of an exemplary incision electrode device 120. The incision electrode device 120 has a flexible ring 122 into which a single ring-shaped wire electrode 128 is incorporated. A flexible shaft 124 connects the flexible ring 122 to the handle 126. Electrical leads (not shown) pass through shaft 124 and handle 126 for connecting electrode 128 to pulse generator 110. Simpler embodiments may use only a bare wire annulus as a heating element.

  The flexible ring portion of the device is dimensioned to the desired size of a capsulotomy having a diameter of, for example, about 5 millimeters. Those skilled in the art will appreciate that an annular opening as shown in FIG. 2 is preferred to avoid tearing when the portion of the capsular bag within the opening is moved. The ring-shaped wire electrode 128 delimits the portion of the capsular bag that is directly heated by the excitation of the electrode.

  In order to reduce secondary damage to the incision edge caused by overheating to improve incision strength and stretchability, attenuated pulses of radio frequency (RF) voltage and pulse sequence excite the capsulotomy probe described above May be used to As already known to those skilled in the art, an automated capsulotomy device can be used with viscoelastic material guided to the surgical site to protect the corneal endothelium and maintain the anterior chamber while removing the cataract. Many. When the capsulotomy probe is excited, the resulting heat causes bumping in the viscoelastic material. Boiling can also occur with tissue water. The thermal process in the viscoelastic material near the excited probe can be divided into three steps: bubble nucleation at the beginning of the pulse, then bubble adhesion, and finally bubble collapse.

  Phase changes in viscoelastic materials occur at the nucleation stage, and high power is required to initiate the process. However, when the excited probe element is isolated from the liquid by bubbles, the energy required to maintain a given elevated temperature is significantly reduced. This is due to the significantly reduced heat dissipation caused by the low vapor thermal conductivity compared to the thermal conductivity of the surrounding viscoelastic liquid.

  Then, in various embodiments according to the present invention, radio frequency pulses sent to the capsulotomy probe are attenuated over the duration of each pulse. This intra-pulse attenuation adjusts the power output to the rapidly changing required power to reduce secondary damage to the incision edge caused by overheating. An example of the attenuation shape of the RF pulse is shown in FIG. The initial high voltage of the pulse can be used to quickly cause boiling of the viscoelastic material and tissue water. The pulse amplitude is attenuated at a predetermined rate or according to an experimentally determined shape, so that the temperature at or near the capsulotomy probe causes the penetrating incision to the capsular bag with less thermal damage to the incision edge. It can be maintained at an appropriate level to produce.

  The preferred attenuation ratio or shape depends on a variety of factors including the nature of the given RF energy, the exact configuration of the capsulotomy probe, or the probe. However, those skilled in the art will appreciate that a shape suitable for a given physical configuration can be determined experimentally. For example, the nucleation process caused by various pulse decay shapes can be observed to identify decay shapes that minimize large bubble coalescence around the excited probe. Similarly, the incisions themselves are free of undue damage, such as capsular expandable damage, and can be observed directly to determine their shape of effectively incising the lens capsule.

  FIG. 6 is a process flow diagram illustrating a method for performing a capsulotomy utilizing the principles described above. The process begins with the insertion of a capsulotomy probe as shown at block 610 into the anterior chamber and placement of the probe into the incision in contact with the anterior lens capsule as shown at block 620. . The wide variety of optional capsulotomy probe configurations that can be used is merely provided so that the probe can be excited with pulsed RF energy.

  Then, as indicated at block 630, at least one RF pulse is delivered to the eye via the capsulotomy probe. The transmitted RF pulse has a predetermined attenuation shape such that the power level of the transmitted RF pulse is substantially attenuated over the duration of the RF pulse. “Substantially attenuated” simply means that power attenuation along the path of the pulse has been systematically and intentionally performed. One skilled in the art understands that the generation and transmission of pulsed RF energy for a physical load is inherently inaccurate, and transmission power uncertainty and pulse rate variations are inevitable. However, in systems using the intrapulse attenuation technique according to the present invention, the degree of attenuation over a given pulse is greater than these normal uncertainties and variations.

  In some cases, the predetermined attenuation shape may attenuate the power level of the transmitted RF pulse to at least one third, eg, 3 dB, over the duration of the RF pulse. In other cases, the degree of attenuation may be, for example, a more substantial 10 dB, 20 dB, or 30 dB. As mentioned above, the specific attenuation shape applied to a given surgical situation may be pre-determined experimentally, the start of the transmitted RF pulse is used to avoid large bubble adhesions and the lens It may be designed to produce bubble nucleation in the eye so that the trailing portion is sufficiently damped to avoid overheating of the sac.

  Multiple pulses of RF voltage can be used to provide more flexible control of the incision energy delivered to the surgical site and to reduce secondary damage caused by thermal degeneration of the tissue. The duration of these pulses and the timing between them can be designed based on the concept of thermal relaxation time and is often used to estimate the time required for heat to transfer directly from a superheated tissue region. (See, for example, B. Choi and AJ Welch et al., “Analysis of thermal relaxation during laser irradiation of tissue”, Las. Surg. Med. 29, 351-359 (2001)). The characteristic thermal relaxation time of the tissue is suitable to maintain the thermal effect of a sealed capsulotomy to a highly localized area, so that the heated viscoelasticity and the time between a series of pulses during which the tissue is cooled Is a useful guide for determining the maximum length of a given RF pulse.

  In conjunction with or in addition to the attenuation of the RF voltage within an individual pulse as described above in connection with FIGS. 4 and 6, the “overall” attenuation shape reduces thermal damage caused by heat absorption. Can be superimposed on a pulse sequence as shown in FIG. 7 (FIG. 7 shows the power shape of the pulse sequence, while FIG. 4 shows the voltage shape of the pulse with internal pulse attenuation). This overall attenuation shape may be considered to define an “inter-pulse” attenuation relative to the “in-pulse” attenuation shown in FIG. As shown in FIG. 7, each second and subsequent pulse in the illustrated sequence is generally attenuated relative to the previous pulse. Thus, the energy of each pulse is attenuated compared to the previous pulse. By way of example only, the initial power level of each of a series of pulses may be attenuated by 20 percent relative to the previous power level (approximately 1 dB), while the power level between pulses is Attenuated over the course, for example by a half or more. The series of pulses shown has only a monotonically decaying pulse, but other sequences may have several subsequences of pulses, each second and subsequent pulses in each subsequence being Although substantially attenuated relative to the previous pulse, the power level may be “reset” to a higher level at the beginning of each subsequence.

  FIG. 8 illustrates another method for attenuating the energy carried by each of a series of pulses delivered to the eye. In the series of pulses shown in FIG. 8, the amplitude of each of the series of pulses is substantially equal, but the duration of each of the second and subsequent pulses is reduced relative to the previous pulse. In addition to the reduced pulse duration, the time between pulses is also varied so that the effective value of power delivered to the eye at any particular interval is attenuated by a suitable shape. Similar to the technique described in connection with FIG. 7, the technique shown in FIG. 8 may be combined with the intra-pulse attenuation shape described above so that the amplitude of each of the series of pulses is a continuation of the pulse. Attenuated over time.

  In some systems, only interpulse attenuation or only intrapulse attenuation may be used, while in others, both techniques may be used. In addition to local and global attenuation of the magnitude of the RF voltage, the modified pulse length, duty cycle, etc., make the RF power output even more accurate, the power required at various stages of the thermal process. Can be used to adjust. Furthermore, the power configuration described above can be modified to enhance the function of tissue water bumping as an incision mechanism to further reduce thermal damage. (The capsular bag contains water. If the heating rate is fast enough, the tissue will experience water bumping, which creates a localized high pressure, for example stress, in the tissue due to tissue confinement. Such localized stress can serve a function in tissue anatomy, so the incision mechanism is a combination of thermal and mechanical effects, and secondary damage to the tissue is compared to a simple thermal incision. And can be reduced.)

  FIG. 5 illustrates functional elements of a pulse generator 110 according to some embodiments according to the present invention. The pulse generator 110 has a main power supply 510 that can be operated from an external AC power supply (eg, 120 volts, 60 Hz) or a DC power supply. The pulse generator 530 generates an RF pulse from the main power source 510 controlled by the control circuit 520. The RF high intensity pulse is supplied to the dissecting electrode device 120 through the lead wire 550. User interface 540 provides the operator with a suitable mechanism for operating pulse generator 110 (e.g., a switch or touch screen input) and suitable feedback (e.g., device status). Further details of a high-intensity pulsed electric field generator that can be easily constructed by the techniques described herein are provided in US Patent Application Publication No. 2007/0156129 published July 5, 2007. The entire contents of which are hereby incorporated by reference.

  In certain embodiments according to the invention, the pulse generator 110 is configured to send at least one radio frequency (RF) pulse to the capsulotomy probe, wherein the sent RF pulse is the power of the sent RF pulse. The level has a predetermined attenuation shape that is substantially attenuated over the duration of the RF pulse. In other embodiments, the pulse generator 110 may perform a series of one or more radio frequency (RF) pulses so that each of the series of subsequent pulses is substantially attenuated relative to the previous pulse. Configured to send to probe. Yet another embodiment is configured to provide both features whereby both intra-pulse attenuation shapes and inter-pulse attenuation shapes are applied to a series of pulses.

  The foregoing descriptions of various embodiments of capsulotomy devices and methods of using these devices have been given for purposes of illustration and illustration. Of course, those skilled in the art will appreciate that the invention may be practiced otherwise than as specifically described herein without departing from the essential characteristics of the invention. Accordingly, the present embodiment is considered to be illustrative and non-restrictive in all respects, and all modifications within the meaning and equivalent scope of the appended claims are included therein. Is considered to be.

Claims (22)

A method for making a capsulotomy,
Inserting a capsulotomy probe into the anterior chamber of the eye;
Placing a portion of the capsulotomy probe in contact with the anterior lens capsule of the eye;
Sending at least one radio frequency (RF) pulse to the eye through the capsulotomy probe, wherein the RF pulse sent is such that the power level of the RF pulse sent is a continuation of the RF pulse. A method having a predetermined attenuation shape that is substantially attenuated over time.   The method of claim 1, wherein the predetermined attenuation shape is an attenuation shape such that the power level of the transmitted RF pulse is attenuated by at least one-half over the duration of the RF pulse.   The method of claim 1, wherein the predetermined attenuation shape is an attenuation shape such that the delivered RF pulse causes bubble nucleation in the eye.   Sending at least one RF pulse to the eye includes a sequence of two or more RF pulses such that the energy of each of the second and subsequent pulses is substantially attenuated relative to the energy of the immediately preceding pulse. The method of claim 1 comprising sending to:   The method according to claim 4, wherein the amplitude of each of the second and subsequent pulses is substantially attenuated with respect to the amplitude of the immediately preceding pulse.   The amplitude of each of the series of second and subsequent pulses is substantially equal to the amplitude of the series of first pulses, and the length of each of the series of second and subsequent pulses is substantially shorter than the length of the immediately preceding pulse. The method of claim 4. A method for making a capsulotomy,
Inserting a capsulotomy probe into the anterior chamber of the eye;
Placing a portion of the capsulotomy probe in contact with the anterior lens capsule of the eye;
Sending a series of two or more radio frequency (RF) pulses to the eye through the capsulotomy probe so that the energy of each of the second and subsequent pulses is substantially attenuated relative to the energy of the previous pulse. Sending.   The method according to claim 7, wherein the amplitude of each of the series of second and subsequent pulses is substantially attenuated with respect to the amplitude of the immediately preceding pulse.   The amplitude of each of the series of second and subsequent pulses is substantially equal to the amplitude of the series of first pulses, and the length of each of the series of second and subsequent pulses is substantially shorter than the length of the immediately preceding pulse. The method of claim 7.   8. The method of claim 7, wherein the energy of each of the series of subsequent pulses is attenuated by at least 20 percent relative to the energy of the previous pulse.   8. The method of claim 7, wherein each transmitted RF pulse has a predetermined attenuation shape such that the power level of the transmitted RF pulse is substantially attenuated over the duration of the RF pulse. A capsulotomy probe configured for insertion into the eye through the incision;
A pulse generator electrically connected to the capsulotomy probe and configured to send at least one radio frequency (RF) pulse to the capsulotomy probe, wherein the transmitted RF pulse is transmitted A capsulotomy device having a predetermined attenuation shape such that the power level of the generated RF pulse is substantially attenuated over the duration of the RF pulse.   13. The capsulotomy device of claim 12, wherein the predetermined attenuation shape is an attenuation shape such that the power level of the transmitted RF pulse is attenuated by at least one half over the duration of the RF pulse.   The capsulotomy device according to claim 12, wherein the predetermined attenuation shape is an attenuation shape in which the transmitted RF pulse causes bubble nucleation in the eye.   The pulse generator is configured to deliver a series of two or more RF pulses to the eye such that the energy of each of the series of subsequent pulses is substantially attenuated relative to the energy of the previous pulse. Item 13. A capsulotomy device according to Item 12.   16. The capsulotomy device according to claim 15, wherein the amplitude of each of the second and subsequent pulses is substantially attenuated relative to the amplitude of the immediately preceding pulse.   The amplitude of each of the series of second and subsequent pulses is substantially equal to the amplitude of the series of first pulses, and the length of each of the series of second and subsequent pulses is substantially shorter than the length of the immediately preceding pulse. Item 16. A capsulotomy device according to Item 15. A capsulotomy probe configured for insertion into the eye through the incision;
A series of two or more pulse generators electrically connected to the capsulotomy probe and in which the energy of each of the second and subsequent pulses is substantially attenuated relative to the energy of the immediately preceding pulse And a pulse generator configured to deliver a radio frequency (RF) pulse to the capsulotomy probe.   19. The capsulotomy device according to claim 18, wherein the amplitude of each of the second and subsequent pulses is substantially attenuated relative to the amplitude of the immediately preceding pulse.   The amplitude of each of the series of second and subsequent pulses is substantially equal to the amplitude of the series of first pulses, and the length of each of the series of second and subsequent pulses is substantially shorter than the length of the immediately preceding pulse. The capsulotomy device according to claim 18.   19. The capsulotomy device of claim 18, wherein the energy of each of the series of second and subsequent pulses is attenuated by at least 20 percent relative to the energy of the previous pulse.   19. The capsulotomy device of claim 18, wherein each transmitted RF pulse has a predetermined attenuation shape such that the power level of the transmitted RF pulse is substantially attenuated over the duration of the RF pulse.

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